1. Field of the Invention
The present invention relates to a tape heating apparatus used in a bookbinding apparatus for automatically gluing or bookbinding a sheet bundle.
2. Related Background Art
It is already known to provide an on-line system in which a series of operations from image formation on a sheet to bookbinding of imaged sheets are continuously performed in a line.
Such an on-line system as shown in FIG. 5 includes a reading and supply apparatus 100 for supplying sheets one by one, an image forming apparatus 200 for forming an image on the supplied sheet, a bookbinding apparatus 300 for gluing a sheet bundle comprised of a plurality of imaged sheets, and a sorting apparatus 400 for sorting the imaged sheets, which apparatuses are connected with each other.
The bookbinding apparatus 300 shown in FIG. 6 includes a sheet convey apparatus 500, a sheet aligning apparatus 600, a tape heating apparatus 700A, a plurality of tape reels 800a, 800b, a book-bond bundle convey apparatus 900 and a plurality of stackers 1000a, 1000b.
In the bookbinding apparatus 300, the imaged sheet not to be book-bound is passed through a path 501; whereas, the imaged sheet to be book-bound is conveyed to the sheet aligning apparatus 600 through a path 502. In this case, a flapper 503 closes the path 501 and opens the path 502.
FIG. 7 shows the sheet aligning apparatus 600 in detail. The imaged sheet sent from the path 502 is discharged onto an align tray 602 by a pair of convey-in rollers 601. In this case, the sheet is guided by upper guides 603a, 603b, 603c and a lower guide 604.
The sheet discharged on the align tray 602 is conveyed along the tray 602 by an align paddle 605 rotated in an anti-clockwise direction, so that a tip end of the sheet abuts against tip end reference shutters 606a, 606b. Further, lateral edges of the sheet are regulated by a fixed align fence 607a and a movable align fence 607b (movable in directions shown by the double-headed arrow). In this way, the tip ends and lateral edges of the sheets discharged on the align tray 602 are aligned with each other at predetermined positions on the align tray 602. When the aligning of a predetermined number of imaged sheets on the align tray 602 is finished, left and right fixed grippers 608a and movable grippers 608b (movable in directions shown by the double-headed arrow) of a sheet bundle convey apparatus 608 waiting at a sheet bundle pinching position (near a tip end of the align tray 602) are operated to pinch the aligned sheet bundle 307, as shown in FIG. 8A.
Then, as shown in FIG. 8B, the tip end reference shutters 606a, 606b are retarded and the conveyance of the sheet bundle 307 by means of the grippers 608a, 608b is started. In this case, the sheet bundle 307 is supported by guides 609a, 609b, and 609c moved in synchronous with the grippers 608a, 608b. Incidentally, at the time when the conveyance of the sheet bundle 307 is started, stop fingers 610a, 610b are positioned as shown in FIG. 7 to temporarily store further imaged sheets discharged onto the align tray 602.
When a trail end of the sheet bundle 307 leaves the align tray 602, as shown in FIG. 8C, the tip end reference shutters 606a, 606b are returned to their initial positions. Further, the stop fingers 610a, 610b are returned to their original positions shown in FIG. 6, with the result that the temporarily stored imaged sheets are dripped onto the align tray 602.
FIG. 10 shows a tape supply apparatus 611. A bind tape T wound around the tape reel 800a or 800b is fed out by a pair of feed rollers 612 and is cut by a tape cutter 613 by a predetermined length. The cut bind tape T is supplied, by a pair of convey rollers 614, to a tape convey apparatus (carriage) 615 waiting at a tape receiving position (position X1 in FIG. 11). Incidentally, the tape convey apparatus 615 includes a plurality of pairs of rollers 616-618.
The tape convey apparatus 615 which has received the bind tape T at the tape receiving position is shifted to a tape transferring position (position X2 in FIG. 11), where the bind tape T is fed out. As shown in FIG. 12, the bind tape T fed out from the tape convey apparatus 615 is set on front tape guides 704, 705 (FIGS. 6 and 11) of a main heater (first heating means) 701 of the tape heating apparatus 700A by a pair of convey rollers 619.
FIG. 14 shows a construction of the bind tape T set on the tape guides 704, 705. A thick hot melt adhesive layer B1 is coated on one surface of the bind tape T at a central portion along a longitudinal direction thereof and thin hot melt adhesive layers B2 are coated on the same surface of the bind tape on both sides of the adhesive layer B1. When the bind tape T is set on the tape guides 704, 705, the main heater 701 waiting at the waiting position is shifted to a bookbinding position, thereby starting the pre-heating of the bind tape. As a result, the thick hot melt adhesive layer B1 is melted. FIG. 12 shows such a melted condition.
A tip end (bound end) of the sheet bundle 307 conveyed by the gripers 608a, 608b is urged against the bind tape T which is being heated by the main heater 701. As a result, the melted hot melt adhesive B1 on the bind tape T penetrates between the sheets of the sheet bundle, thereby gluing the sheet bundle 307. Thereafter, side heaters (second heating means) 702, 703 waiting at their waiting positions are shifted to a bookbinding position, where the both side portions of the bind tape T are pressurized and heated by the side heaters. As a result, thin hot melt adhesive layers B2 are melted, thereby binding the bind tape T to front and rear surfaces of the sheet bundle 307. In this way, the bookbinding operation is completed.
Thereafter, the book-bound sheet bundle (book-bound article) 307 is conveyed by the grippers 608a, 608b from the bookbinding operation to a transferring position to the book-bound bundle convey apparatus 900 to transfer the book-bound sheet bundle 307 to the book-bound bundle convey apparatus 900. FIG. 9A shows a condition that the book-bound sheet bundle 307 is conveyed to the transferring position and stopped there. When the book-bound sheet bundle 307 reaches the transferring position, receiving trays (rotary trays) 901a, 901b of the book-bound bundle convey apparatus 900 which were positioned at a home position shown in FIG. 6 are shifted to the transferring position, thereby permitting the receiving trays to receive the book-bound article (this condition is shown in FIG. 9B). Incidentally, the receiving trays 901a, 901b are shifted rocked upwardly from the home position (waiting position) shown in FIG. 6 to the transferring position. When the book-bound article 307 is rested on the receiving trays 901a, 901b, the book-bound article 307 is released from the grippers 608a, 608b, and the grippers are returned to the sheet pinching position of the align tray 602 (this condition is shown in FIG. 9C).
After the grippers 608a, 608b returning to the sheet pinching position leave the book-bound article 307, the receiving trays 901a, 901b on which the book-bound article 307 was rested are rocked downwardly to the waiting position of FIG. 6. Meanwhile, the book-bound article 307 is transferred from the receiving trays 901a, 901b to a feed-in tray (horizontal tray) 902. When the receiving trays 901a, 901b are returned to the waiting position, the book-bound article 307 starts to be contained into the stacker 1000a or 1000b by the book-bound bundle convey apparatus 900.
First of all, the feed-in tray 902 is positioned in the vicinity of an upper end of the stacker (this condition is shown in FIG. 13A). Then, the feed-in tray 902 is shifted toward the stacker to position the book-bound article 307 above the stacker (this condition is shown in FIG. 13B). Then, the feed-in tray 902 is lowered to contain the book-bound article 307 into the stacker (this condition is shown in FIG. 13C).
In the case of the conventional bookbinding apparatus 300, the side heaters 702, 703 of the tape heating apparatus 700A perform the heating/pressurizing operation at one time at a position in the vicinity of the bound edge 307a of the sheet bundle 307 as shown in FIG. 15 or at a position spaced apart from the bound edge 307a of the sheet bundle 307 by a predetermined distance as shown in FIG. 16.
However, as shown in FIGS. 15 and 16, if a thickness (t) of the sheet bundle 307 is smaller than a width of the thick hot melt adhesive layer B1, when the heating/pressurizing operation is effected at the position shown in FIG. 15, since the thick hot melt adhesive layer B1 exists on the front and rear surfaces of the sheet bundle 307, gaps H are created between the thin hot melt adhesive layers B2 and the front and rear surfaces. As the result, both side portions T2, T3 of the bind tape T may not be adhered to the front and rear surfaces of the sheet bundle 307 completely. On the other hand, when the heating/pressurizing operation is effected at the position shown in FIG. 16, since the thick hot melt adhesive layer B1 existing on the front and rear surfaces of the sheet bundle 307 cannot be reduced, swollen portions R are formed in the vicinity of the bound edge 307a of the book-bound article 307, thereby worsening the appearance.